Event ID - 21177

According To Microsoft:The failure may be due to a shortage of resources, probably memory resources. If it is not a memeory resource problem, it may be the result of a bad configuration or storage corruption.

Resolution:
View the web filter configuration to verify that it is valid.Free up memory resources by closing open applications.If the problem persists, and a backup exists, use the ISA Server Restore option to overwrite the corrupt configuration. To do this, in the console tree of ISA Server Management, right-click the name used to manage the ISA Server configuration, and then click Restore. For details about restoring an ISA Server configuration, see ISA Server Help. If you are unable to restore the configuration, or doing so does does not solve the problem, you should reinstall ISA Server. Before reinstalling, you must first uninstall ISA Server using the remove program applet avaialable from Control Panel. When you uninstall, you lose all the configuration parameters. Reinstalling ISA Server without first uninstalling the previous copy does not resolve this problem.